It is common practice in the field of cash registers to record the printing done by a transfer thermal print head. The film supporting the transferred ink leaves a transparent zone from where the ink has disappeared. This means that a negative record is available of the printing that has been done. In existing recording devices, the ink-carrying film travels between two wheels: a take-up wheel and a pay-out wheel; the two wheels being contained in a cassette-forming housing. The cassette makes it possible to install the film in the printer and to remove it therefrom, and above all the cassette can be reused when reading the film medium. It thus constitutes a log of the operations performed by the printer.
Nevertheless, reading is generally performed in the same zone of the cassette as that where the film co-operates with the print head, thus restricting the scope of such reading and sometimes requiring a special apparatus to be used.